A Th2 cytokine, IL-4, induces various chemokines from epidermal keratinocytes which play crucial roles in the pathogenesis of skin disorders such as atopic dermatitis. In contrast, the role of IFN-gamma, a Th1 cytokine, on eosinophilic skin inflammation is unclear. This study investigated the effects of IFN-gamma on IL-4-induced production of eotaxin-3/CCL26, a potent chemoattractant to eosinophils, in normal human epidermal keratinocytes (NHEK). When the cells were stimulated with IL-4 and IFN-gamma simultaneously, IL-4-induced CCL26 production was attenuated. In contrast, prior stimulation with IFN-gamma enhanced IL-4-induced CCL26 production. NHEK constitutively expressed type 1 IL-4 receptor, and expression at the cell surface was upregulated by stimulation with IFN-gamma. This upregulation resulted in an enhanced IL-4-mediated cellular signal. These results indicate that IFN-gamma has opposite effects on IL-4-induced CCL26 production in NHEK depending on the time of exposure. Thus, changes in IL-4R expression by IFN-gamma might modulate eosinophilic skin inflammation. (C) 2008 Elsevier Inc. All rights reserved.